many other Points, or be parallel to so many other Lines, or converge to
so many other Points, either accurately or without any sensible Error.
And the same thing will happen, if the Rays be reflected or refracted
successively by two or three or more Plane or Spherical Surfaces._

The Point from which Rays diverge or to which they converge may be
called their _Focus_. And the Focus of the incident Rays being given,

                  Implementations should prefer to express Gateway conditions
                  using the `GatewayConditionType` and `GatewayConditionReason`
                  constants so that operators and tools can converge on a common
                  vocabulary to describe Gateway state.


                  Known condition types are:


                  * "Accepted"
                  * "Programmed"